What is the ruling on praying on the roof of the Haram and in the courtyard of the Haram when it is not crowded with worshippers?

The prayer is valid as long as the worshipper inside the mosque can see the Imam or those behind him, or hear the takbirat, and can follow him. It is preferable to be close to the Imam and complete the front rows. However, there is no harm in praying in another part of the mosque, such as the basement or the second floor, if that prevents harm or increases one's khushu' (devotion).